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Room block attrition calculator

Attrition is the one line in a hotel contract that can turn a sold-out weekend into a loss. Put your block, your clause and your pickup in below and the exposure is exact. Nothing here is stored or sent anywhere.

Your attrition exposure$6,80418 unfilled rooms × 2 nights × $189
Rooms you must fill
80 of 100
Pickup so far
62%
Rooms from clear
18 rooms
Block at full pickup
$37,800

An 80% clause means the hotel bills you for rooms below 80 — whether or not anyone sleeps in them. Rooms your attendees book outside the block do not count toward it.

What the number above is telling you

An attrition clause is a promise about occupancy, not about attendance. You told a hotel that a certain share of the rooms you reserved would be booked and paid for, and the hotel priced your rate and released the inventory on the strength of that promise. If the rooms go unfilled the hotel is not obliged to absorb the gap, so the contract hands it to you.

The reason this catches experienced organizers is that the two numbers deciding it are set at different times. The block size and the clause are agreed months out, when the only honest answer to how many rooms is a guess. The pickup happens in the last few weeks, when your audience finally commits. Anything you learn in between arrives too late to change the contract, and the safest-looking choice at signing, blocking generously so nobody is left without a room, is precisely the choice that creates the exposure.

Read your clause for these four things

  • The threshold. 80% is the common ask. 90% is aggressive. Anything above 90% deserves a conversation before you sign, not after.
  • The basis. Damages calculated on the full room rate cost far more than damages calculated on lost profit. Ask for lost profit.
  • The measurement window. Attrition measured cumulatively across the whole block is far more forgiving than attrition measured night by night, where a soft Sunday can trigger a bill even though the weekend sold out.
  • The resell credit. If the hotel fills your unbooked rooms with someone else, they have lost nothing. A resell clause says those rooms are deducted from your damages. It is a normal request and it is often granted simply because nobody asks.

The rooms you never see

Every pickup report has a blind spot. Your block records the attendees who used your link, and nothing else. The families who split into a rental, the couple who found a cheaper rate two exits down, the crew that booked an extended-stay for the week: all of them travelled to your event, all of them paid for lodging, and none of them appear anywhere in your numbers or reduce your attrition liability by a cent.

In a market we measured for a real event weekend, roughly 70% of the lodging money was committed inside the final 30 days, and about 31% of it landed in properties that were part of a sold-out block. Both figures point the same way: the demand exists and it is timed late. If your block is the only thing you offer, most of that demand routes around you.

That is why we built the second calculator. Sizing a block sensibly is half the answer, and knowing what falls outside it is the other half. Work out how many rooms to contract for or read the longer guide to room blocks and attrition.

Common questions

What does 80% attrition mean?

It means you have promised the hotel that at least 80% of the rooms you blocked will actually be booked and paid for. If you block 100 rooms on an 80% clause, 80 of them are your responsibility. Fill 62 and you are billed for the other 18 at the contracted rate, for every night the block covers, whether anyone sleeps in them or not.

How is attrition damage actually calculated?

The common formula is unfilled rooms below the threshold, multiplied by the contracted room rate, multiplied by the nights held. Some contracts charge the lost profit rather than the full rate, and some measure attrition per night rather than across the whole block, so read which one you signed. The difference can be several times the number.

Do rooms booked outside the block count toward attrition?

Usually not, and this is the trap. An attendee who books the same hotel through a booking site instead of your block link is generally invisible to your pickup report. Some contracts include a review clause that lets you claim those rooms if you can document them; most organizers never ask for one.

What is the difference between the cutoff date and the attrition clause?

The cutoff date is when unbooked rooms are released back to the hotel to sell. Miss it and you lose the inventory and the rate. The attrition clause is the financial promise about how much of the block gets filled, and it survives the cutoff. Releasing rooms at cutoff does not automatically reduce what you owe under attrition unless the contract says so.

How can I reduce attrition risk?

Contract a smaller block than you expect to fill and add rooms later if pickup is strong, negotiate the threshold down or measure it across the whole block rather than per night, ask for a resell credit so rooms the hotel sells anyway are deducted, and make the block the easiest option your attendees see at the moment they are deciding, which is at your checkout rather than in an email three weeks later.

The overflow does not have to be someone else’s revenue

Bookend puts real places to stay on your confirmation page, at the moment your attendee is deciding, and pays you a share of every booking it produces. It costs you nothing and you can switch it off any time.

See what your share would be

More free tools

Room block size calculatorWork out how many rooms to contract for — and how many nights your attendees will book somewhere else.